Alkylation of hydrocarbons



Patented Jan. 19, 1943 2,308,560 ALKYLATION OF HYDROCARBONS I Don R.Carmody, Whlting,.lnd., and Edmond L. dOuville, Chicago, Ill., assignorsto Standard g1 Company, Chicago, 111., a corporation of diana NoDrawing. Application December 30, 1939,

Serial No. 311,950

19 Claims.

This invention relates to the production of normally liquid hydrocarbonsfrom normally gaseous hydrocarbons and relates more particularly to thealkylation of isoparafllnic hydrocarbons with olefinic hydrocarbons inthe presence of a catalyst.

In the modern operation of a petroleum refinery, it is customary tosubject the heavier fractions of crude oil to a cracking operation inorder to produce additional amounts of gasoline. In the course of such aprocess, varying amounts of normally gaseous hydrocarbons are produced,these hydrocarbons including those having two, three and four carbonatoms per molecule, both saturated and unsaturated, as well as methaneand hydrogen. Until comparatively recent years, these gases wereconsidered in the nature of waste gases, and were to a large extent usedas fuel gases or discarded, although portions of the least volatilegases, such as the butanes and butenes, might be incorporated in thegasoline itself in limited amounts. It has since been realized thatthese normally gaseous hydrocarbons are a valuable source material forthe synthesis of gasoline range hydrocarbons, and under properconditions, will yield motor fuels or motor fuel blending stocks of highantiknock value characterized 'by the presence of large amounts ofbranched chain or aromatic hydrocarbons. The processes employed includepolymerization (with hydrogenation, if desired), alkylation, etc. boththermal and catalytic of which catalytic alkylation is perhaps the mostdesirable due to the comparative ease of formation of valuable saturatedbranched chain hydrocarbons without further treatment.

It is an object of this invention to provide an improved process for thealkylation of isoparaffinic hydrocarbons and, more specifically,isobutane with normally gaseous olefins to produce saturatedbranched-chain hydrocarbons within the gasoline boiling range. Anotherobject of our invention is to provide an improved catalyst for efiectingsuch an alkylation reaction. A still further object is to provide acatalytic process for the production of high antiknock motor fuel fromnormally gaseous hydrocarbons of two, three and four carbon atoms permolecule. A further object is to provide an alkylation process utilizingethylene as the olefi'nic stock. Another object of this invention is toprovide an alkylation process wherein the activity of the catalyst ismaintained within a definite range throughout the process. Furtherobjects and advantages will become apparent as the description of theinvention proceeds.

Briefly stated, our invention contemplates the alkylation of anisoparaflln, particularly isobutane, with one or more mono-olefinshaving two, three or four carbon'atoms per molecule in the presence ofan aluminum halide-hydrocarbon complex, particularly an aluminumchloridehydrocarbon complex. The isoparafiln and olefins can come fromany source, as for instance refinery gases or partially dehydrogenatedconstituents of natural gas. Moreover, they need not be (and usually arenot) pure hydrocarbons but may be mixtures of hydrocarbons iallingwithin this general class. The isobutane, for example, can be anordinary "plant butane cut from the absorption of gases or thedebutanization of gasoline and may contain various amounts of normalbutane and isobutane, as well as the corresponding olefins, and may alsocontain minor amounts of three and five carbon atom hydrocarbons, due toimperfect separation. The isobutane may also be obtained as the oil gasfrom the selective polymerization of the butylene present in a "plantbutane fraction, or from the decomposition of hydrocarbons of highermolecular weight during an isomerization, catalytic cracking orcatalytic reforming operation. The source and purity of the feed stockis immaterial within reasonable limits, and dilution with unreactivegases, such as normal butane can be tolerated although it is desirableto use as feed stock a gaseous hydrocarbon containing as large an amountof the reactive constituent as is practical. The feed stock should befree of water, ammoniacal substances and the like.

Our process can be carried out either batchwise or in a continuousoperation and the conditions employed will vary to some extent dependingupon the reacting ingredients. Generally speaking, it is desirable touse temperatures of from about 0 F. to about 212 F. and preferably fromabout 50 F. to about F., and to employ pressures of from'aboutatmospheric to about 1000 pounds per square inch gauge, preferably fromabout 50 to about 500 pounds per square inch gauge; the pressure in anycase being sufficient to maintain the reactants in the liquid phase atthe temperature employed.

The catalyst used forms an important part of this invention. The use ofaluminum chloride or aluminum bromide for the promotion of catalyticreactions, such as condensation, polymerization, cracking, alkylation,isomerization, etc. is well known. However, the alkylation reactionordinarily proceeds with too great violence in the presence of purealuminum chloride or aluminum bromide to permit the controlledproduction of desired products. We have found that if anhydrous aluminumchloride or aluminum bromide is reacted with a liquid hydrocarbon toform a complex having certain critically defined characteristics, amodified catalyst is produced which is effective for promoting thealkylation of isoparaflinic hydrocarbons with oleflnes without too greatviolence.

This catalyst is especially suitable for use when ethylene is employedas the alkylating hydrocarbon, although it gives equally good resultswith other normally gaseous oleiinic hydrocarbons. Moreover, theethylene may form only a small part of the alkylating gas used, beingdiluted with ethane, hydrogen and methane, and still alkylateisoparafllns in the presence of this catalyst. Although propylene andthe butylenes may be reacted with isoparaflins in the presence of acatalyst such as sulfuric 'acid with comparative ease, it has been foundextremely dimcult to promote the similar reaction with ethylene underlike conditions. Therefore, a catalyst which will permit the utilizationof ethylene, and particularly dilute ethylene in the production ofsaturated hydrocarbons of branched-chain configuration is especiallyvaluable. The isohexane produced by our process is primarily2,3,dimethyl butane of extraordinarily high octane number which isobtained only in limited amounts by thermal alkylation and not at all bysulfuric acid alkylation. It should be understood, however, that the useof propylene or the butylenes for this process is included within thescope of this invention.

The catalyst is prepared by refluxing an excess of normally liquidhydrocarbon with anhydrous aluminum chloride until the aluminum chloridehas been converted to the liquid complex, stirring the reactantsmeanwhile. Gaseous hydrogen chloride is added at a rate suillcient tokeep the hydrocarbon saturated to promote the reaction. Although thenormally liquid hydrocarbons may contain minor amounts of aromatics andoleflns, they are preferably aromatic and olefin-free.

- Parafllnic or cycloparafllnic hydrocarbons having six or more carbonatoms per molecule have been found to be preferable, and the feed stockmay be a mixture of hydrocarbons of this general description, any of thepure hydrocarbons falling within this classification, or a mixture ofany of the saturated hydrocarbon of this nature. At the end of therefluxing and stirring period, the aluminum chloride has formed acomplex with the hydrocarbon, a heavy oily liquid, usually yellow to redin color. The hydrocarbons remaining as an upper layer are separatedfrom the complex. In place of aluminum chloride, aluminum bromide can beused for the formation of the catalytic complex or a mixture of aluminumchloride and aluminum bromide can be employed to yield a mixed aluminumchloride complexaluminum bromide complex suitable for promotingcatalytic alkylation.

The exact nature of the formation of the complex by the reaction ofanhydrous aluminum chloride or aluminum bromide with a liquidhydrocarbon in the presence of a promoter such as gaseous hydrogenchloride or hydrogen bromide, is not completely understood. Thereappears to be, however, a considerable variation in the effectiveness ofthe complexes formed by this reaction when various types of hydrocarbonsare employed as feed stock. While a large variety of hydrocarbons andhydrocarbon stocks can be used, paramnic hydrocarbons and oils rich inparaillnic hydrocarbons are in general distinctly preferable, Naphthenesor naphthene-containing hydrocarbons are also advantageous. Attemptshave been made to analyze the organic compounds present in the complexby breaking down the complex into its component parts but the productsare of such complex nature that they defy exact analysis. All of thecomplexes, however, have a measurable heat of reaction when the complexis added to water. We have discovered that the most effective aluminumhalide-hydrocarbon complex catalysts for the promotion of the alkylationof isoparafilnic hydrocarbons with oleflnic hydrocarbons are thosewhich, in the case of aluminum chloride complexes, have heats ofhydrolysis between the limits of 60 large calories per gram atom ofactive aluminum and large calories per gram atom of active aluminum, andin the case of aluminum bromide complexes between 67 and 82 largecalories per gram atom of active aluminum. By maintaining the activityof the catalyst within these limits an alkylation process can be carriedout continuously with increased yield of product having the desiredgasoline characteristics. By the expression "active aluminum" as usedabove, in the tables below, in other places in this specification, andin the claims of this application is meant the aluminum content of thehydrolyzable aluminum compounds in the liquid phase aluminumhalide-hydrocarbon complex. Inactive aluminum compounds, such as, forexample, the hydroxide that is present in a partially hydrolyzedcomplex, is not included in the term gram atom of active aluminum! Theheat of hydrolysis can be determined by any well known calorimetricmethod wherein the temperature rise occasioned by the addition of onemol of the complex to approximately mols of water can be measured.

Table I' shows a series of typical experiments made with aluminumchloride-hydrocarbon complexes of different activities as indicated bytheir heats of hydrolysis. It can be readily seen that complexes havingheats of hydrolysis within the above range, preferably in the upper partof that range, are particularly advantageous for the alkylationreaction.

Table I Cstalyst-AlCh-hydrocarbon complex Heat of Heat of Heat ofhydrolysis hydrolysis hydrolysis 67 CaL/gr. 59 5 CaL/gr 54 Cal/gr. atomof atom of atom of active active active aluminum aluminum aluminumIsofiaraiiin, parts by wt.

-O4 290 290 290 Olefin, parts by wt. (Calla)... 84 82 84 Temperature, F14-24 18 14-24 Wt. Heroent yield (on oleiln) 161. 0 144. 0 117. 8 Distlation of product vol.

percents9. 2 64. a as. 3

Table II compares two typical experiments, one using pure aluminumchloride as the catalyst and the other an active aluminumchloride-hydrocarbon complex. The pure aluminum chloride catalyst yieldsa relatively high percentage of products, i. e., C5, C1, C9 and heavierproducts, resulting from secondary reactions, such as cracking,polymerization, etc. The product from the aluminum chloride-hydrocarboncomplex catalyst is essentially only primary alkylate.

\ Table 1! Catalyst AlClr-hydrocarbon complexheat of Pure A101;hydrolysis 67 Cal/gr. atom of; active aluminum Isobutane, parts by wt467 390 Ethyle 0, parts by wt. 92 94 Temperature, F 105 105 Pressure,lbs.lsq. in.-. 155-180 70-150 Duration (hrs.) 6. 6 5 Stabilized product,parts by wt 200 235 Wt. percent yield (on olefin) 218 250 Distillationof product v01. percent Table III compares the hexanes produced frompure aluminum chloride catalyst and the hexanes from an aluminumchloride-hydrocarbon complex having a heat of hydrolysis of 67 largecalories per gram atom of active aluminum. In the second case, themodified activity of the catalyst has yielded a purer product with ahigher octane number than that from the aluminum chloride.

In carrying out the alkylation process olefins, for example ethylene,propylene and/or butylenes, together with an iso-parafiln, for exampleisobutane, are added to the complex at a temperature of from about 50 toabout 175 F., for example 105 F., and at pressures of from about 50pounds per square inch gauge to about 500 pounds per square inch gauge,for example 145 pounds per square inch gauge. The mixture is stirred toinsure intimate contact between the reactants and the catalyst and thetime of reaction can vary of course with temperature, intimacy ofcontact, composition of gases, etc. over a wide range, from a fewseconds to several hours.

By carrying out the alkylation reaction under a superimposed hydrogenpartial pressure of 50 to 1000 pounds per square inch, preferably aboutperature conditions ranging from -35 F. to 400 F. the life or activityof the catalyst may be greatly extended by thus maintaining the heat ofhydrolysis in the optimum range.

It is preferable that there be maintained an excess of iso-parafiin overthe amount of olefins present, and in any case the iso-paraflln shouldbe present in at least equimolecular proportions as compared with theolefins since an excess of olefins leads to the formation of highboiling products of unsaturated nature. The mol ratio of isoparafllns toolefins should preferably be within the range from about 3:1 to about 6:1.

During the alkylation reaction the activity of the complex catalyst isreduced through involved and little understood side reactions whichinitially reduce the heat of hydrolysis of the complex below the heat ofhydrolysis found efiective for the optimum promotion of alkylation. Inorder to prevent this the activity of the catalyst can be maintained bythe addition thereto of regulated amounts of fresh aluminum chloride oraluminum bromide. By the judicious employment of activating material acontinuous process may be set 200 to 800 pounds per square inch, andunder temup wherein the alkylation is carried out under conditionsyielding anOptimum amount of gasoline of high octane number. We havefound the most effective aluminum chloride complex to have a heat ofhydrolysis of about 65 to about 75 large calories per gram atom ofactive aluminum while an aluminum bromide complex having a heat ofhydrolysis of about 72 to about 82 large calories per gram atom ofactive aluminum will yield optimum conversion.

In the event that a mixture of aluminum chloride and aluminum bromidecomplexes are employed, the heat of hydrolysis should be that determinedby multiplying the optimum heat of hydrolysis for the aluminum chloridecomplex by the mol fraction of aluminum chloride and that for thealuminum bromide complex by the mol fraction of aluminum bromide andadding the two. Similarly, the desirable range of heat of hydrolysis maybe obtained by substituting the maximum and minimum heats of hydrolysisfor the optimum heats of hydrolysis in the above.

Other isoparaflins, for example, isopentane or isohexane, may be used inplace of isobutane. The use of these isoparaflins is determined not bytheir reactivity or availability, since they are equally suitable withisobutane for this purpose and may be found in substantial quantities inpetroleum refinery naphthas and gasolines, but upon the economic factorsof the process. They form one of the valuable consituents of motorfuels, since'they boil in the lower range of the gasoline hydrocarbonsand have the desirable characteristic of high octane number. Therefore,as a practical matter, isopentane or isohexane will not ordinarily beused for the synthesis of high antiknock fuels unless there is a surplusabove that readily utilizable, or unless the isoheptanes, isooctanes orisononanes which would result from the alkylation are considered moredesirable than the isopentane or isohexane itself. The use of isopentaneand higher molecular weight isoparaflins as a parafllnic feed stock forthis alkylation process is therefore contemplated within the scope ofthis invention.

This application is a continuation-in-part of our copending application,Serial No. 287,088. filed July 28, 1939;

We claim:

1. A method of converting an isoparaflinic hydrocarbon into hydrocarbonsor higher molecular weight which comprises alkylating said hydrocarbonwith at least one normally gaseous olefinic hydrocarbon in the presenceof acatalyst comprising a complex Iormed by the reaction of ahydrocarbon with an aluminum halide of the class consisting of aluminumchloride and aluminum bromide in the presence oi a hydrogen halide ofthe class consisting of hydrogen chloride and hydrogen bromide, saidcomplex having a heat of hydrolysis of from about 60 to about 75 largecalories per gram atom of active aluminum in the case of aluminumchloride and from about 67 to about 82 large calories per gram atom ofactive aluminum in the case of aluminum bromide.

2. A method of converting an isoparaflin into hydrocarbons of highermolecular weight which comprises alkylating said isoparaflln with atleast one normally gaseous olefin in the presence of a catalystcomprising a liquid complex formed by the reaction of a paramnichydrocarbon oil and aluminum chloride in the presence of hydrogenchloride, said complex having a heat of hydrolysis of from 60 to 75large calories per gram atom of active aluminum.

3. A method of converting an isoparaflinic hydrocarbon into hydrocarbonsof higher molecular weight which comprises alkylating said isoparaffinichydrocarbon with a normally gaseous olefin in the presence of a catalystcomprising a complex formed by the reaction of at least one hydrocarbonand aluminum bromide in the presence of a hydrogen halide of the classconsisting of hydrogen bromide and hydrogen chloride, said complexhaving a heat of hydrolysis of from about 72 to about 82 large caloriesper gram atom of active aluminum.

4. A method of converting isobutane into hydrocarbons of highermolecular weight which comprises alkylating said isobutane with at leastone normally gaseous olefin in the presence of a catalyst comprising acomplex formed by the reaction of a hydrocarbon liquid with an aluminumhalide of the class consisting of aluminum chloride and aluminum bromidein the'presence of a hydrogen halide of the class consisting of hydrogenchloride and hydrogen bromide, said complex having a heat of hydrolysisof from about 60 to about 75 large calories per gram atom of activealuminum in the case of aluminum chloride and from about 67 to 82 largecalories per gram atom of active aluminum in the case of aluminumbromide.

5. A method of converting an isoparaflinic hydrocarbon into ahydrocarbon of higher molecular weight which comprises alkylating saidisoparaflinic hydrocarbon with an ethylene-containing gas in thepresence of a catalyst comprising a complex formed by the reaction of ahydrocarbon and aluminum chloride in th resence of a hydrogen halide ofthe class consisting of hydrogen bromide and hydrogen chloride, saidcomplex having a heat of hydrolysis of from about 60 to about 75 largecalories per gram atom of active aluminum.

6. A method of converting isobutane into a hydrocarbon of highermolecular weight which comprises alkylating said isobutane with anethylene-containing gas in the presence of a catalyst comprising acomplex formed by the reaction of a hydrocarbon and aluminum chloride inthe presence of a hydrogen halide of the class consisting of hydrogenbromide and hydrogen chloride, said complex having a heat ofhydrolaaoaseo ysis of from about 60 to about 75 large calories P r gramatom of active aluminum.

7. A method according to claim 4 in which said hydrocarbon liquid ispredominantly'paraffinic.

8. A method according to claim 4 in which said hydrocarbon liquid ispredominantly cycloparaiilnic. Y

9. A method of alkylating an isoparafllnic hydrocarbon with at least oneolefinic hydrocarbon which comprises reacting said isoparafllnichydrocarbon and said at least one oleflnic hydrocarbon in thepresence'ot a catalyst comprising a complex formed by the reaction of ahydrocarbon material with an aluminum halide of the class consisting ofaluminum chloride and aluminum bromide in the presence of a hydrogenhalide oi. the class consisting of hydrogen chloride and hydrogenbromide and maintaining the activity of said catalyst by the addition ofa sufilcient amount or an aluminum halide-containing material of highheat or hydrolysis to maintain the heat of hydrolysis of said catalystwithin the range of from about 60 to about 75 large calories per gramatom or active aluminum in the case of aluminum chloride and from about67 to about 82 large calories per gram atom of active aluminum in thecase of aluminum bromide.

10. A method of converting an isoparafllnic hydrocarbon intohydrocarbons of higher molecular weight which comprises contacting saidisoparaflinic hydrocarbon with at least one normally gaseous oleflnichydrocarbon in the presence or a catalyst comprising a complex formed bythe reaction of a hydrocarbon with an aluminum halide of the groupconsisting of aluminum chloride and aluminum bromide in the presence ofa hydrogen halide of the group consisting of hydrogen chloride andhydrogen bromide. said complex having a heat of hydrolysis oil fromabout 60 to about 75 large calories per gram atom of active aluminum inthe case of aluminum chloride and from about 67 to about 82 largecalories per gram atom of active aluminum in the case of aluminumbromide under a hydrogen partial pressure of from about 50 pounds to1000 pounds per square inch, at a temperature adapted to promote thealkylation of said isoparaflinic hydrocarbon with said at least onenormally aseous olefinic hydrocarbon.

11. A method of converting an isoparaflinic hydrocarbon intohydrocarbons of higher molecular weight which comprises contacting saidisoparafllnic hydrocarbon with at least one normally gaseous olefinichydrocarbon in the presence of a catalyst comprising a complex formed bythe reaction of a hydrocarbon with an aluminum halide of the groupconsisting of aluminum chloride and aluminum bromide in the presence ofa hydrogen halide of the group consisting of hydroen chloride andhydrogen bromide, said complex-having a heat of hydrolysis of from about60 to about 75 large calories per gram atom of active aluminum in thecase oi! aluminum chloride and from about 67 to about 82 large caloriesper gram atom of active aluminum in the case of aluminum bromide under ahydrogen partial pressure of from about 200 pounds to 800 pounds persquare inch, at a temperature adapted to promote the alkylation of saidisoparaflinic hydrocarbon with said at least one normally gaseousolefinic hydrocarbon.

12. A method of converting isobutane into hydrocarbons of highermolecular weight which comprises contacting said isobutane with at leastone normally gaseous olefin in the presence of a catalyst comprising acomplexformed by the reaction of a hydrocarbon liquid with an aluminumhalide of the group consisting of aluminum chloride and aluminum bromidein the presence oi. a hydrogen halide of the group consisting ofhydrogen chloride and hydrogen bromide, said complex having a heat ofhydrolysis of from about 60 to about 75 large calories per gram atom ofactive aluminum in the case of aluminum chloride and from about 67 to 82large calories per gram atom of active aluminum in the case of aluminumbromide under a hydrogen partial pressure of from about 50 to 1000pounds per square inch at a temperature adapted to promote thealkylation or said isobutane with said at least one normally aseousolefin.

13. The method of making 2,3,dimethy1 butane which method comprisesalkylating isobutane with ethylene in the presence of a catalystcomprising a liquid complex formed by the reaction of a hydrocarbonliquid with an aluminum halide of the class consisting of aluminumchloride and aluminum bromide in the presence of a hydrogen halide ofthe class consisting of hydrogen chloride and hydrogen bromide, saidcomplex havin a heat of hydrolysis of from about 60 to about 75 largecalories per gram atom of active aluminum in the case of aluminumchloride and from about 67 to 82 large calories per gram atom ofaluminumin the case or aluminum bromide.

14. The method of claim 13 which includes the steps of eflecting saidalkylation at a temperature within the approximate range of 50 to 175 F.and under a pressure sufflcient to maintain the reactants in the liquidphase at the temperature employed.

15. The method of claim 13 which includes the step of charging a molratio oi. isobutane to ethylene within the approximate range or 3:1 to6:1 to the alkylation step.

10. The method of claim 13 wherein the alkyiation is eifected at atemperature within the approximate range of to 175 F. at a pressurewithin the approximate range of 50 to 500 pounds per square inchsuflicient' to maintain the reactants in the liquid phase at thetemperature employed and wherein an excess of isobutane is maintained ascompared with ethylene in the alkylation step.

17. The method of obtaining 2,3,dimethylbutane by alkylating isobutanewith ethylene which method comprises alkylating isobutane with ethylenein the presence of a catalyst comprising a liquid complex formed by thereaction of a hydrocarbon liquid with an aluminum halide of the classconsisting of aluminum chloride and aluminum bromide in the presence ofa hydrogen halide of the class consisting of hydrogen chloride andhydrogen bromide, said complex having a heat of hydrolysis of from aboutto about large calories per gram atom of active aluminum in the case ofaluminum chloride and from about 67 to 82 large calories per gram atomof active aluminum in the case of aluminum bromide, maintaining at leastan approximatel equimolecular proportion of isobutane to ethylene in thealkylating step, effecting the alkylation at a temperature within theapproximate range of 50 to 175 F. under a pressuresufllcient to maintainthe reactants in liquid phase at the temperature employed and separatingproducts of the alkylation reaction to obtain a stabilized product.

18. The method of claim 17 wherein the predominating component or thestabilized product is a Ca component and wherein the Co componentconsists chiefly of 2,3,dimethylbutane.

19. The method of claim 17 wherein the reaction temperature is in thegeneral vicinity of F., the reaction pressure is within the generalvicinity of pounds per square inch and the stabilized product consistschiefly of 2,3,di-

methylbutane.

' DON R. CARMODY.

EDMOND L. nOUVILLE.

